Spin detector for golf games

ABSTRACT

A golf game including a ball capturing net resiliently suspended in spherical form relative the tee point and biased laterally by two side take-up cylinders. Deflection of the net by the momentum and spin of an impacting ball unwinds the cylinders. The outputs of a piezo-electric signal generators activated by the unwinding of each cylinder are integrated, compared and the difference displayed by a galvonometer calibrated to indicate slice or hook of the ball.

United States Patent Conklin SPIN DETECTOR FOR GOLF GAMES [72] Inventor: Robert M. Conklin, Muskegon, Mich.

[73] Assignee: Brunswick Corporation [22] Filed: Dec. 14, 1970 [21] Appl. No.: 97,554

[52] US. Cl. ..273/l85 R, 73/432 R, 273/181 F,

[451 Sept. 12, 1972 1,657,913 1/1928 Barnett ..273/l8l K FOREIGN PATENTS OR APPLICATIONS 372,743 4/1932 Great Britain ..273/l85 R Primary Examiner-George J. Marlo Attorney-Donald S. Olexa, Jerome M. Teplitz, John G. Heimovics, William G. Lawler, Jr. and Hofgren, Wegner, Allen, Stellman & McCord 57 ABSTRACT A golf game including a ball capturing net resiliently suspended in spherical form relative the tee point and biased laterally by two side take-up cylinders. Deflection of the net by the momentum and spin of an impacting ball unwinds the cylinders. The outputs of a piezo-electric signal generators activated by the unwinding of each cylinder are integrated, compared and the difference displayed by a galvonometer calibrated to indicate slice or hook of the ball.

6 Claims, 4 Drawing Figures 1 SPIN DETECTOR FOR GOLF GAMES BACKGROUND OFTI'IE INVENTION 1. Field of Invention This invention relates to an apparatus used in a golf game that may be played indoors wherein a novel target means and sensing means associated therewith are employed to detect the spin on a driven golf ball.

2. Description of the Prior Art 2. Description of the Prior Art The ever increasing upsurge of the popularity of the game of golf has resulted in severe crowding of existing outdoor facilities. As a result, there have been numerous proposals for indoor golf games wherein an entire game of 18 holes may be played indoors. Such indoor golf games customarily involve tee areas from which a ball may be hit to be intercepted by a target. Suitable data acquisition means are interposed between the tee and the target and provide information relative to the initial trajectory, speed and spin of a driven golf ball. This information is then fed into a computer which will ascertain how far the ball would have traveled'had it not struck the target. One of the factors taken into consideration is the amount of spin imparted to a driven golf ball which dictate whether or not the ball which has been hit will travel in a *sliced" or hooked" trajectory.

In the past, it has been known to measure spin by means of a rebound type of target. This type of target requires that a ball, after hitting a target, he allowed to rebound to a second target area wherein, through different sensing means, the angle deviation between the actual angle in which the golf ball rebounds off the first target and the angle of rebound ofa golf ball having no spin imparted thereon(normally equal to the angle of impact) is measured.

While such golf games embodying such a spin measuring means have been very satisfactory in measuring the amount of spin imparted to a driven golf ball, the require that there be a rebound becomes a disadvantage since additional space to house rebound sensing means away from the target is required. Also, since spin is measured after the rebound, more time is required for data acquisition than if spin were to be measured prior to a rebound. Finally, an errantly rebounding ball missing a spin detecting means may return to thetee to strike a golfer.

SUMMARY OF THE INVENTION The principal object of this invention is to provide a new and improved apparatus for use in an indoor golf game which measures the spin imparted on a driven ball without requiring a rebound to do so, thereby minimizing space requirements.

The spin measuring apparatus includes a tee for a golf ball, a target means against which a ball strikes when driven directly from the tee, and means for measuring the impulse imparted to the target means from a golf ball having spin thereon. The impulse is measured in a direction normal to the line of travel of the driven golf ball. The impulse measuring means includes means mounting the target for movement in a direction normal to the flight of a driven golf ball so that the impulse tends to cause the target to move in said direction a distance proportional to the spin imparted to the golf ball and means for measuring the force which the target has imparted to the mounting means after being struck by the golf ball. After the impulse has been measured, an output signal representative of the measured impulse in generated.

An exemplary embodiment of the invention employs a concave spherical target formed of a net wherein the sphere has its center at the tee. The force that the ball imparts to the target is measured by two transducers which are operatively connected to the mounting means on opposite sides of the target. The system is arranged so that the impulse imparted to the target by a ball in the direction of its line of flight is eliminated by means of a differential circuit associated with both transducers.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevation of a golf apparatus made according to the invention;

FIG. 2 is a horizontal section of the golf apparatus taken generally along line 2-2 of Fig. 1;

.FIG. 3 is an enlarged fragmentary plan view of an impulse measuring device employed in the invention; and

FIG. 4 is an electrical schematic diagram of a spin measuring and indicating circuit employed in the golf apparatus. 1

DESCRIPTION OF THE PREFERRED EMBODIMENT An exemplary embodiment of an indoor golf game apparatus embodying the invention is illustrated in FIGS. 1 and 2 and is seen to comprise a tee point 10 from which a golf ball may be driven and target ineans, generally designated 12, against which a ball impacts when driven from the tee 10. The target 12 is made from a rectangular piece of netting 14 capable of cap turing a golf ball and is located in front of the tee 10 generally transverse to an intended line of flight of a ball hit therefrom.

The net 14 forms a portion of a sphere having its center at the tee point 10. This configuration insures that any point on the target 12 which is struck by a golf ball driven from tee 10 will be normal to the line of flight of the ball for purposes which will become more apparent hereinafter.

The net 14 is mounted by a pair of vertical mounting means, generally designated 16, and each supporting one end of the net 14. Each mounting means 16 is generally seen to include a vertical shaft 20, secured at its top and bottom to a stationary surface and a cylinder 22 mounted concentrially about the shaft 20 for rotation thereabout. The ends of the net 14 are secured to respective ones of the rotatable cylinders 22. Looking at Fig. 2, the lefthand end of the net 14 is wound around the left-hand cylinder 22 in a clockwise direction while the right-hand end of the net 14 is wound about the right-hand cylinder 22 in a counterclockwise direction. To keep the net 14 taut at all times each cylinder 22 is spring biased by means not shown about the vertical shaft 20 in a direction tending to pull the net 14 toward the tee point 10.

Maintenance of the desired spherical configuration of the net 14 is accomplished by a plurality of vertically curved brace members 24. The brace members 24 are attached to the back of the net 14 and pull the net 14 backwards to present a concave spherical surface to the tee point 10. Each brace member 24 has a coil spring 26 attached at each end thereof which are fixedly secured to top and bottom stationary surfaces respectively, such as a ceiling and a floorv of a room. The spring constant of each of the springs 26 is sufficiently weak that a ball impacting against the net 14 will cause brace members 24 along the net 14 to yield but is strong enough to restore the net 14 to the desired spherical configuration.

:A golf ball driven in such a way as to impart spin to the same bears two forms of kinetic energy. The first form, hereinafter referred to as linear momentum, is that energy content of the ball present due to moving along its line of flight. The second, hereinafter referred to as angular momentum, is due to the rotation of the ball about its center due to the impartation of spin thereto. Therefore, when a golf ball having spin imparted thereto when struck from the tee impacts against the target 12, the linear momentum of the golf ball will drive the net backwardly and the angular momentum will cause a movement of the net in a plane normal to the golf ball line of flight and in a direction in the plane corresponding to the direction of rotation of the ball about its center. The former movement of the net may be regarded as a velocity impulse while the latter may be regarded as a spin impulse.

The rearward motion of the net will tend to force each of the spring biased cylinders 22 to unwind the net while loading up the associated spring (not shown). The spin impulse, to the extent that it includes side spin responsible for hook or slice, will tend to cause one of the spring biased cylinders 22 to unload while the other will be further loaded. Since the velocity impulse is much greater than a spin impulse, both of the spring biased cylinders 22 will tendto unwind thereby loading up their respective springs, however, to a different degree depending upon the nature and magnitude of the side spin. That is, because the target 12 is spherical with respect to the tee point and a ball hit from the tee point will always impact against the same normal to the surface of the target at the point of impact, the loading of the cylinders 22 due to the velocity impulse will be equal and the loading due to the spin impulse, if any, will be unequal.

By way of example, looking at Fig. 2, if a righthanded golfer drives a golf ball from the tee point and has imparted a slicing side spin on the golf ball, (i.e., a spin in a clockwise direction looking down at Fig. 2), the following sequence of events occurs: (1) the golf ball strikes the net 14 normal thereto; (2) the net 14 will tend to be forced backwards due to the velocity impulse normal to the net 14; (3) the net 14 will tend to be forced in a right-hand direction normal to the flight of a golf ball from the tee 10 due to the impulse associated with the slicing side spin on the golf ball; (4) the left-hand cylinder 22 will have an unwinding force associated therewith in response to the combined velocity and impulse components acting simultaneously on the net 14; and (5 the right-hand cylinder 22 will have an unwinding force associated therewith which is less than the force associated with the lefthand cylinder in response to the combined velocity and spin impulse components acting simultaneously on the net 14.

As a result, the following conditions at the cylinders 22 will exist. For the left-hand cylinder 22,

IL =I,.-i'I, (Equation and the right-hand cylinder,

1R=1L-I, (Equation 5 where:

IL, is equal to the total impulse applied to the lefthand cylinder IR, is the total impulse applied to the right-hand 1O cylinder 25 plied to the left-hand cylinder 22 and the total impulse applied to the right-hand cylinder 22 which may be accomplished by ascertaining the unwinding force applied to the cylinders 22.

in order to measure the unwinding force in which each end of the net 14 exerts on its respective concentric shaft 22, pair of impulse measuring means, generally designated 30, one associated with each cylinder 22, are provided as shown in Fig. 3. The impulse measuring means measures the force or impulse which tends to unwind each cylinder 22.

One measuring means 30, shown in Fig. 3, is seen to generally comprise an arm 32 fixedly attached to the right-hand cylinder 22 and extending outwardly therefrom in a normal abutting relation with a transducer 34 such as a piezo-electric crystal. When the cylinder is caused to rotate in a clockwise direction due to the striking of golf ball, the arm 32 is momentarily pressed hard against the piezo-electric transducer 34 which causes an electrical impulse proportional to the 5 pressure applied thereto. It is apparent that the greater the unwinding force due to the golf ball impacting the target the greater pressure the arm 32 exerts on the piezo-electric transducer 34, which produces a greater amount of electrical charge.

Turning now to Fig. 4, the electrical circuits comprising both measuring means 30 are shown in greater detail. Each circuit is identical to the-other and therefore only one shall be described in detail. Each circuit is seen generally to include means for sensing stress or strain such as the piezo-electric transducer 34, an emitter follower amplifier generally designated 36, and an operational amplifier in an integrating circuit, generally designated 38. The circuit is appropriately powered as shown.

When pressure is applied to the transducer 34 by arm 32, a signal is caused to flow out of the transducer 34. This signal is amplified and integrated by amplifiers 36 and 38, respectively.

5 A galvanometer 40 is connected across the outputs of both integrating circuits 38 in a differential manner and serves the purpose of subtracting the strength of the amplified and integrated transducer signals generated by each measuring means 30 wherein the difference represents the amount of impulse imparted to the target as a function of spin.

For example, assuming that the uppermost measuring circuit shown in Fig. 4 is associated with the righthand cylinder 22 and the lowermost circuit shown in Fig. 4 is associated with the left-hand cylinder 22 and further assuming that a right-handed golfer has. hit a ball from the tee in such a way as to impart a slicing side spin thereto as mentioned above, it will be appreciated that the magnitude of the signal at the output of the integrating circuit 38 associated with the righthand cylinder 22 will be less than the magnitude of the output of the integrating circuit 38 associated with the left-hand cylinder 22. This difference will cause galvanometer 40 to deflect in a particular direction determined by the polarity of the imbalance and an amount determined by the magnitude of the imbalance which will therefore serve as an indication of the nature and magnitude of the side spin imparted to the ball.

It will also be appreciated thatif the imbalance were of a polarity opposite of that mentioned in the preceding paragraph, the direction of deflection of the galvanometer 40 would be opposite that for the preceding example and further that if there were no imbalance, correspondingto a no side spin condition, there would be no deflection of the galvanometer.

Also provided in conjunction with each measuring means 30 as shown in Fig. 4 is a reset button 42 which, when closed, is operative to discharge each integrating circuit 38 to reset the apparatus for the next shot.

Those skilled in the art will appreciate that indicating means other than the galvanometer 40 may be employed. For example, a so-called ball spot projector responsive to known circuitry receiving the output signals from the integrating circuits 38 could be used in lieu thereof. Furthermore, the reset button 42 need not be manually operated as shown but could be operated automatically by golf known in the art.

While the disclosed embodiment is directed to the determination of side spin, it will be appreciated that the principles enunciated herein can also be employed in the measurement of backspin or overspin either alone or in conjunction with side spin simply by providing force measuring means responsive to spin impulses in the vertical direction imparted to the net 14. By the same token, while the use of a spherical target permits a ball to strike the targets surface in a direction normal thereto for each shot so that linear momentum impulses on opposite sides of the net cancel out for simplicity of measurement, the principles of the invention are equally applicable to non-spherical targets. That is, a target shaped in such a way that the ball will not impact against the targets surface in a direction normal thereto can be used although additional means for eliminating any vector component of the velocity impulse normal to ball flight may be required. For example, a planar target may be employed along with means game computer reset means for sensing the angle of deviation of a ball hit from thetee from a line extending to the tee and normal to the target and the sensed angle of deviation utilized in computation to eliminate sideways impetus imparted to the target due to the velocity of the ball.

I claim:

1. In an indoor golf game, an apparatus for measuring the spin imparted to a driven golf ball comprising:

a tee area from which a golf ball may be driven;

target means for receiving the impact of a ball driven directly to said target means from the tee; and

means for measuring the force exerted upon said target means by the spin on the golf ball impacting thereon.

2. The apparatus of claim 1 wherein said force measuring means includes means mounting the target means for movement in a direction generally normal to the line of flight of a driven golf ball so that said target will be displaced upon impact by the angular impulse of a golf ball having a spin thereon a distance in said generally normal direction proportional to the spin on the impacting golf ball; and

means for measuring the. force which the target means exerts on the mounting means as a result of such displacement.

3. In an indoor golf game, an apparatus for measuring the spin imparted to adriven golf ball comprising:

a tee area from which a golf ball may be driven;

target means for receiving the impact of a ball driven directly from the tee;

means for retaining said target in a preselected position and means operationally coupled to said retaining means for sensing therethrough forces upon said target means exerted exclusively in a direction substantially normal to the flight path of the ball impacting the target.

4. In an indoor golf game, an apparatus for measuring the spin imparted to a driven golf ball comprising:

a tee from which a golf ball may be driven; a spherical target means for receiving the impact of a ball driven directly from said tee,

means resiliently mounting the spherical target means with its focus and said tee in coincidence whereby the angular impulse associated with a golf ball having spin thereon imparted to said target means upon impact of the ball tends to cause the target means to move in a plane substantially normal to the direction of travel of a ball hit from the tee; and

means for measuring the force which the target means exerts on said resilient mounting means as a result of being struck by a spinning golf ball.

5. The apparatus of claim 4 wherein said spherical target means is made from a net which is capable of capturing a golf ball. I

6. In an indoor golf game, an apparatus for measuring the spin imparted to a driven golf ball comprising:

a tee from which a golf ball may be driven;

a spherical target formed out of netting against which a ball strikes when driven directly from the tee, said spherical target having its focus at the tee and so presenting a surface normal to the direction of the flight of a golf ball driven from the tee;

a pair of vertical means mounting the target at each end thereof, each mounting means including a fixed vertical shaft having a concentric cylinder mounted for rotation thereabout, said net being secured to said cylinder and wound thereabout and each cylinder being spring biased about the fixed shaft in opposite directions to keep the get exerts on each cylinder after the target has been struck by a golf ball and providing a signal representative thereof; and

means for subtracting the signals representative of the two unwinding forces thereby providing a signal representative of the sidespin imparted to the golf ball. 

1. In an indoor golf game, an apparatus for measuring the spin imparted to a driven golf ball comprising: a tee area from which a golf ball may be driven; target means for receiving the impact of a ball driven directly to said target means from the tee; and means for measuring the force exerted upon said target means by the spin on the golf ball impacting thereon.
 2. The apparatus of claim 1 wherein said force measuring means includes means mounting the target means for movement in a direction generally normal to the line of flight of a driven golf ball so that said target will be displaced upon impact by the angular impulse of a golf ball having a spin thereon a distance in said generally normal direction proportional to the spin on the impacting golf ball; and means for measuring the force which the target means exerts on the mounting means as a result of such displacement.
 3. In an indoor golf game, an apparatus for measuring the spin imparted to a driven golf ball comprising: a tee area from which a golf ball may be driven; target means for receiving the impact of a ball driven directly from the tee; means for retaining said target in a preselected position and means operationally coupled to said retaining means for sensing therethrough forces upon said target means exerted exclusively in a direction substantially normal to the flight path of the ball impacting the target.
 4. In an indoor golf game, an apparatus for measuring the spin imparted to a driven golf ball comprising: a tee from which a golf ball may be driven; a spherical target means for receiving the impact of a ball driven directly from said tee, means resiliently mounting the spherical target means with its focus and said tee in coincidence whereby the angular impulse associated with a golf ball having spin thereon imparted to said target means upon impact of the ball tends to cause the target means to move in a plane substantially normal to the direction of travel of a ball hit from the tee; and means for measuring the force which the target means exerts on said resilient mounting means as a result of being struck by a spinning golf ball.
 5. The apparatus of claim 4 wherein said spherical target means is made from a net which is capable of capturing a golf ball.
 6. In an indoor golf game, an apparatus for measuring the spin imparted to a driven golf ball comprising: a tee From which a golf ball may be driven; a spherical target formed out of netting against which a ball strikes when driven directly from the tee, said spherical target having its focus at the tee and so presenting a surface normal to the direction of the flight of a golf ball driven from the tee; a pair of vertical means mounting the target at each end thereof, each mounting means including a fixed vertical shaft having a concentric cylinder mounted for rotation thereabout, said net being secured to said cylinder and wound thereabout and each cylinder being spring biased about the fixed shaft in opposite directions to keep the netting taut whereby the angular impulse associated with a golf ball having spin thereon in combination with the impulse associated with the velocity of said ball is imparted to the target thereby tending to cause each cylinder to unwind an amount proportional to the spin and velocity imparted to the golf ball; a pair of means, one associated with each cylinder, for measuring the unwinding force which the target exerts on each cylinder after the target has been struck by a golf ball and providing a signal representative thereof; and means for subtracting the signals representative of the two unwinding forces thereby providing a signal representative of the sidespin imparted to the golf ball. 